[Participation of neurons of the midbrain reticular formation of the cat in conditioned reflex activity].
Spike discharges of mesencephalic reticular formation neurons were investigated during classical and instrumental conditional reflexes in chronic experiments on cats. Neurons were divided into several functional groups according to patterns of their responses. Two groups of neurons produced continuous tonic spike discharges. One of them was activated by positive conditional stimuli and did not respond to the same stimulus after extinction. Another group was involved in reaction only after extinction. Thus the neurons of these two groups developed additional tonic ascending action not only during fulfillment of conditional reflex but under its internal inhibition too. Neurons of the third group revealed double phasic responses: the first--to sound and the second--in connection with initiation of the conditioned movement. They decreased the level of the background and evoked activity during differentiation and extinction. Initial changes of reticular neuron responses were similar under conditioning and under pseudoconditioning. It is concluded that mesencephalic reticular formation takes an active and differential participation in elaboration, fulfillment and internal inhibition of classical and instrumental conditional reflexes.